1T-2H Mixed-Phase MoS 2 Stabilized with a Hyperbranched Polyethylene Ionomer for Mg 2+ /Li + Co-Intercalation Toward High-Capacity Dual-Salt Batteries.

Dual-salt magnesium/lithium-ion batteries (MLIBs) benefit from fast lithium ion diffusion on the cathode side while providing safety due to the dendrite-free Mg 2+ stripping/plating mechanism on the anode side. Bulk MoS 2 (B-MoS 2 ), as a cathode for magnesium-ion batteries (MIBs), suffers from low conductivity and relatively van der Waals gaps and, consequently, resists against divalent Mg 2+ insertion due to the high Coulombic interactions. In MLIBs, it exhibits a Daniell-cell type mechanism with the sole accommodation of Li + . In this paper, the synthesis of a 1T/2H mixed-phase MoS 2 (MP-MoS 2 ) modified with a hyperbranched polyethylene ionomer, I@MP-MoS 2 , for high-capacity MLIBs with a distinct Mg 2+ /Li + co-intercalation mechanism is reported. Benefiting from the enhanced conductivity (due to 53% metallic 1T phase), expanded van der Waals gaps (79% expansion compared to B-MoS 2 , 1.11 vs 0.62 nm), and enhanced interactions with THF-based electrolytes following the modification, I@MP-MoS 2 shows a dramatically increased Mg 2+ storage compared to its parent analogue (144 mAh g -1 vs ≈2 mAh g -1 at 20 mA g -1 ). In MLIBs, I@MP-MoS 2 is demonstrated to exhibit remarkable specific capacities up to ≈270 mAh g -1 at 20 mA g -1 through a Mg 2+ /Li + co-intercalation mechanism with 87% of capacity retention over 200 cycles at 100 mA g -1 .